1. Field of the Invention
The present invention relates to a developing device accommodating a developer and an image forming apparatus such as a copier, a printer or a facsimile machine.
2. Description of the Related Art
A developing device performing a developing operation using a two-component developer including toner and carrier consumes the developer and requires replenishment of the developer. The developer to be replenished contains only toner or is toner rich (a state containing more toner than carrier). Thus, toner particles become massed together with relatively weak cohesion to cause soft blocking in a toner replenishment path. The soft blocking may cause incomplete mixing of the developer present in the device with newly supplied developer. Further, supplying the toner with the soft blocking to a developing roller and then to a sheet in a printing process may cause image formation failures such as color unevenness and color streaks.
Japanese Unexamined Patent Publication No. 2002-148915 discloses a developing device with means for preventing soft blocking of a developer to be replenished. This developing device includes a developer conveying member and a toner supplying member. Rotary shafts of the developer conveying member and the toner supplying member are aligned on the same axial line. The objective of an agitator between a developer conveyance region and a toner supply region is to pulverize the massed toner particles and facilitate the mixing of the replenished developer with the developer present in the developing device at a point into which the replenished developer and the developer present in the developing device flows each other. The agitator may, however, cause stagnation of the replenished developer and the developer present in the developing device at their interfluent point, which results in their insufficient mixing.